The invention relates to a motor vehicle with a plurality of control devices that can be activated through an activation element. When the activation element is in a switched-on condition, it emits an ignition signal VZ to the control devices, and when the activation element is in a switched-off condition, it does not emit the ignition signal. The control devices, which are in signal communication with each other, are activated by the ignition signal VZ and deactivated by the absence of the ignition signal VZ.
In motor vehicles of the foregoing description, if the ignition signal fails to reach, e.g., only one of the control devices, this one control device is deactivated while the other control devices are or remain activated. This can have the result that a blown fuse in the ignition circuit of a control device will cause the one control device to become deactivated although the ignition is not in the switched-off condition. The deactivated state of the one control device can affect the proper functioning of the vehicle.
The object of the invention is to provide a device that allows the functions of a motor vehicle to remain operable safely and substantially without restriction even if the ignition signal VZ fails to reach the input of one of the control devices, as long as the same signal is still being received by one or more of the other control devices.
As a further objective, the invention aims to provide a method by which the functions of a motor vehicle are kept operable safely and substantially without restriction even if the ignition signal VZ fails to reach the input of one of the control devices, as long as the same signal is still being received by one or more of the other control devices.
To meet the foregoing objective, the invention provides the concept that at least one of the control devices is designed so that it is not deactivated by the absence of an ignition signal VZ, if the ignition signal VZ is present in at least one other control device, or if another signal indicating the presence of an ignition signal exists at the one control device. The presence of the ignition signal at the at least one other control device is communicated through a signal connection such as a data bus transmission to the control device that failed to receive the ignition signal. If for example the at least one other control device is an engine control device that regulates the rpm-rate of the engine, the presence of an rpm-signal from the engine, combined with the fact that the engine is running, can be taken as an indication that an ignition signal is present at the engine control device.
In a practical embodiment of the invention, if an ignition signal VZ is received by the at least one other control device, the latter sends a signal through the signal connection or at least emits a signal indicating or representing the presence of an ignition signal.
Advantageous embodiments of the invention use the concept that the control device is not deactivated in the absence of an ignition signal if a signal from at least one other control device is received that indicates or represents the presence of an ignition signal.
It is likewise advantageous if a control device is allowed to send signals through the signal connection only if an ignition signal is present. This has the advantageous result that a control device will send signals only if an ignition signal is present at that particular control device. Thus, the presence of an ignition signal can be detected alone by the fact that signals are being sent through the signal connection. If a control device detects that signals are being sent from another control device, this means that the sending device is activated and that it is receiving an ignition signal.
According to a practical concept of the present invention, control devices in the activated condition send at least one signal through the signal connection or emit at least one signal. It is further practical, if a control device that is not receiving an ignition signal sends a defined signal through the signal connection which indicates that an ignition signal is not present at that particular control device.
According to a further concept of the invention it can be advantageous if at least two of the following control devices are provided in a motor vehicle and are in signal communication with each other:
a control device of a clutch with automated clutch-actuation;
a control device of an engine control;
a control device of a transmission control;
a control device of an anti-slip regulation;
a control device of an anti-lock braking system;
a control device of a traction control arrangement;
a control device of a climate control system;
a control device of a navigation system; or
another control device.
A further advantageous concept of the invention can be used in a motor vehicle that is equipped with an automated clutch, an engine, a transmission, a clutch control device for controlling the automated clutch, and a unit for determining the rpm-rate nmot of the engine, wherein the clutch control is normally activated by an activation element which sends an ignition signal VZ to the clutch control device when the ignition is switched on. According to the invention, even if the clutch control device fails to receive an ignition signal, it nevertheless remains activated as long as an engine rpm-signal indicates that the engine rpm-rate nmot is above a predetermined rpm-limit nlimit.
The following concept of the invention can likewise be used to advantage in a motor vehicle that is equipped with an automated clutch, an engine, a transmission, a clutch control device for controlling the automated clutch, and a further control device, wherein the clutch control device and the further control device are normally activated by an activation element which sends an ignition signal VZ to the control devices when the ignition is switched on. According to the invention, even if the clutch control device fails to receive an ignition signal, it nevertheless remains activated as long as the clutch control device receives a signal from the further control device indicating that an ignition signal VZ is present at the further control device.
Another advantageous concept within the scope of the invention can be used in a motor vehicle that is equipped with an automated clutch, an engine, a transmission, a clutch control device for controlling the automated clutch, and a further control device, wherein the clutch control device and the further control device are normally activated by an activation element which sends an ignition signal VZ to the control devices when the ignition is switched on. According to the invention, even if the clutch control device fails to receive an ignition signal, it nevertheless remains activated as long as the clutch control device receives a signal from the further control device indicating that the further control device is in an activated state.
Yet another advantageous concept within the scope of the invention can be used in a motor vehicle that is equipped with an automated clutch, an engine, a transmission, a clutch control device for controlling the automated clutch, and a further control device, wherein the clutch control device and the further control device are normally activated by an activation element which sends an ignition signal VZ to the control devices when the ignition is switched on. According to the invention, even if the clutch control device fails to receive an ignition signal VZ, it nevertheless remains activated as long as the clutch control device receives a signal from the further control device indicating that an ignition signal VZ is present at the further control device and/or that the engine rpm-rate nmot is above a predetermined rpm-limit nlimit.
Yet another advantageous concept within the scope of the invention can be used in a motor vehicle that is equipped with an automated clutch, an engine, a transmission, a clutch control device for controlling the automated clutch, and a further control device, wherein the clutch control device and the further control device are normally activated by an activation element which sends an ignition signal VZ to the control devices when the ignition is switched on. According to the invention, even if the clutch control device fails to receive an ignition signal VZ, it nevertheless remains activated as long as the clutch control device receives a signal from the further control device indicating that an ignition signal VZ is present at the further control device and/or that the further control device is in an activated state.
Yet another advantageous concept within the scope of the invention can be used in a motor vehicle that is equipped with an automated clutch, an engine, a transmission, a clutch control device for controlling the automated clutch, and a further control device. According to the further inventive concept, at least the first control device, when in the activated state, sends signals through a data bus.
A further advantageous concept within the scope of the invention can be used in a motor vehicle that is equipped with an automated clutch, an engine, a transmission, a clutch control device for controlling the automated clutch, and a further control device. According to the further inventive concept, the first control device sends signals through a data bus, if a signal is present that indicates that the further control device is in an activated state.
The following concept according to the invention can likewise be used in a motor vehicle that is equipped with an automated clutch, an engine, a transmission, a clutch control device for controlling the automated clutch, and a further control device. According to the inventive concept, the first control device sends signals through a data bus if an engine-rpm signal is present indicating that an engine rpm-rate exceeds an rpm-limit.
Under a further advantageous concept of the invention, the first control device sends a starter release signal through the data bus when the transmission is shifted into the neutral position.
It is likewise advantageous according to the invention, if the control device that controls the engine starts up the vehicle engine if a starter release signal is present and an engine-start operation is initiated by the driver.
In the embodiments and concepts described herein, the control device referred to as xe2x80x9cotherxe2x80x9d or xe2x80x9cfurtherxe2x80x9d control device is advantageously represented by one of the following control devices:
a control device of an engine control;
a control device of a transmission control;
a control device of an anti-slip regulation;
a control device of an anti-lock braking system;
a control device of a traction control arrangement;
a control device of a climate control system;
a control device of a navigation system; or
another control device.
It is likewise advantageous if at least one control device is an electronic control device with a microprocessor.
It is further advantageous if the signal connection is a data bus connection. It is particularly useful if the signal connection is a CAN-bus (Central Area Network bus) connection.
It is further practical if at least one of the following elements is used as activation element:
an ignition switch for switching on the ignition of the vehicle;
a vehicle brake operating element, such as a pedal and/or handle;
a transponder code card.
It is further practical if, prior to its deactivation, the control device of the automated clutch moves the clutch into engagement, which has the effect of a parking lock if the transmission is in gear. It is likewise advantageous if a variable predeterminable length of time lies between the engagement of the clutch and the deactivation of the control device. The length of the time interval can be a function of vehicle parameters.
It is likewise practical if the at least one signal which indicates or represents the presence of an ignition signal is constituted by one of the following signals:
an ignition signal VZ 
an activity signal of a control device
an engine rpm-rate signal nmot 
a throttle valve signal
a fuel-injection rate signal
an engine torque signal Mmot 
a wheel rpm-rate signal nwheel 
a transmission rpm-rate signal ntrsm.
A further concept of the invention relates to a method for controlling subsystems in the drive train of a motor vehicle such as an automated clutch, with at least one control device for controlling the operation of the automated clutch and at least one other control device wherein the control devices are activated when a switching element is switched on and deactivated when the switching element is switched off. The inventive method includes at least some of the following steps:
interrogating whether an ignition signal or an engine rpm-rate signal is present at the at least one control device;
leaving the control device activated if at least one of the two signals is present;
emitting no signals from the control unit through a data bus if neither of the two signals is present;
deactivating the control unit if neither of the two signals is present.
A further embodiment of the foregoing inventive method, likewise, relates to the control of subsystems in the drive train of a motor vehicle such as an automated clutch, with at least one control device for controlling the operation of the automated clutch and at least one other control device wherein the control devices are activated when a switching element is switched on and deactivated when the switching element is switched off. The inventive method includes at least some of the following steps:
interrogating whether an ignition signal, engine rpm-rate signal and/or and engine control activity signal is present at the at least one control device;
leaving the control device activated if at least one of the ignition signal, the engine rpm-rate signal, or the engine activity signal is present;
emitting no signals from the control unit through a data bus in the absence of the ignition signal if neither the engine rpm-rate signal nor the engine activity signal is present;
deactivating the control unit in the absence of the ignition signal if neither the engine rpm-rate signal nor the engine activity signal is present.
In a practical embodiment of the invention, the control device is a control device for controlling the automated clutch. Prior to deactivation of the control device the clutch is moved into engagement.
It is likewise advantageous if a waiting time is observed prior to the deactivation of the control device. It is particularly advantageous if a waiting time is observed prior to the engagement of the clutch. The length of either of the waiting periods can be dependent on at least one operating parameter of the vehicle.
The device according to the invention ensures that a safe operation of the automated clutch is maintained if the ignition signal fails to be received at the input of the control device of the automated clutch. A further embodiment ensures a safe switching-on or restarting of the engine after it has been switched off even if at least the control device of the automated clutch is not receiving the ignition signal.
The invention further relates to a motor vehicle with a plurality of control devices which are activated through an activation element which sends out an ignition signal VZ, wherein the control devices are in signal connection with each other and mutually monitor each other, wherein at least one control device is not caused to be deactivated by the absence of an ignition signal VZ as long as an ignition signal VZ is present in at least another control device or if the at least one control device is receiving another signal indicating the presence of an ignition signal.